Alternating potential generator



Aug; 14, 1928. 1,680,377

W. H. T. HOLDEN ALTERNATING POTENTIAL GENERATOR Filed NoYJ 17, 1924 6. may"):

INVENTOR.

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ATTORNEY Patented Aug, 14, 1

UNITED (STATESPATENT; OFFICE.

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PHONE AND TELEGRAPH COMPANY, A. CORPORATION OF NEW YORK.

ALTEBNATING POTENTIAL GENERATOR.

Application filed November, 1924. Serial 180.1750392.

This invention relates to electrical -converting apparatus, for deriving an alternating potential from a direct current potential, or for deriving 5 an alternating current of one frequency from One of the ob ects of this inventionis to produce an alternating potential from a direct current potential by an arrangment employing a hot cathode gas-filled discharge device capable of operating upon relatively low potentials.

Other objects of this invention will be apparent from the following description,

when read in connection with the attached drawing of which Figure 1 shows schematically a simple form of embodiment of the invention; Figs 2 and 3 are variations of the form shown in Fig. 1; and Fig. 4 shows a irenquency converting system.- In Fig; 1, a source of direct current poten tial 1, which, for example, may be a battery, direct current generator or other similar device and in magnitude from 24 to 48 volts, has its positive terminal connected with the impedance 2, the other terminal of which is connected with the anode of the electrical discharge device 3 and also with one of the terminals of .the condenser 5. The negative terminal of the direct current source 1 is con nected with the cathode of the device 3, which is heated from any suitable source such as the battery .4. The cathode is also connected with the condenser 5' sothat the condenser and the discharge device are in parallel. The. alternating current output circuit is connected across the terminalsof .50 the condenser 5, the connection including-the condensers 6 and 7 which prevent the direct current from the source 1 from flowing over the output circuit.

Thedischarge tube, is of the hot cathode and particularly to means to discharge through have had limi gas-filled type. The manner in which this circuit operates to producethe alternating HOLDEN, OF BROOKLYN, NEW YORK, ASSIGNOB TO AMERICAN TELE-' voltage will probably be obvious, The direct current voltage of the'source'l will be impressed across-the impedance 2, and the tube 3 and the condenser 5 in parallel. It Wlll. be seen that as long as the voltage at the tube terminals is too low to produce an appreciable discharge therethrough the condenser will charge up'by the flow of current from the source 1 through the impedance 2. When the voltage at the tube ter-- minals rises to the value required to start an arc aconsiderable current will flow through the tube. As this current increases the drop in potential in the impedance 2 also increases. When this drop reaches a value so as to reduce the voltage acros the electrodes of the tube below a certain critical value, the discharge therethrough will no longer be sustained. After the are has been established the condenser 5 will begin to discharge and a portion of the current through the device 3 will be supplied by: the condenser. When the discharge ceases the condenser 5 will again be charged thtough the impedance 2 until the voltage across the device 3 reaches a break-down value, when the cycle of op-- eration will be repeated. The voltage across the output circuit is of an alternating character, following the voltagechanges of condenser 5. a o v This process obviously requires that the initial break-down potential to start the arc shall be higher than the voltage required to maintain the are after it has started,'and the amount of alternating current energy that can be secured from such a device will depend on the difference between the voltage required to start thearc andthe minimum voltage at which the arc can be maintained. I have found that discharge tubes employ ,ing thoriated tungsten filaments which had been activated by the vaporization ofmagnesium require very low voltages to maintain the arc in comparison with the tubes having non-thoriated filaments. In order to secure the most eflicient operation of a discharge device of this type it is believed that a tube containing pure helium at a pressure of from 50 to 75 millimeters of mercury and having a thoriated tungsten cathode activated by magnesium, as above described, and a graphite anode would render it possible to start the discharge by a potential in the neighborhood of 20 volts and to maintain the arc by a potential as low as five or six volts. The starting and maintenance voltages of other tubes is considerably greater than those men- 1 tioned above.

The arrangements shown in Figs. 2 and 3 illustrate mainly other ways of connecting ,the output circuit with the converting circuit.

Thus in Fig. 2 the alternating current output circuit is connected with the convertingcircuit by the transformer 7 which has its simulates the impedance 2 of Fig. 1. Fig. 3.

primary winding 8 connected with the converting circuit and the secondary winding 9 with the output circuit. The transformer 7 I 5, windings 8 of transformer 7 and condenser 10 is tuned to the frequency to be transferred to the alternating current output circuit. The mode of operation of Figs. 2 and 3 is similar to that of Fig. 1 and needs no further explanation.

Thearrangement shown in Fig. 4 is useful where it is desired to convert an alternating current of one frequency into a sFmilar current of another frequency. The underlying principle employedin this arrangement consists in coverting the alternating current to a direct current and creating therefrom alternating current of the desired frequency.

In thefigure, the source 11 of alternating current is connected with the primary winding 12 of transformer 13 .having a plurality of secondary windings. One of these windings 14 is connected with the cathode 15 of the tube 16,. in order to supply the necessary, heating current. In like manner the wind 'ing 17 is connected with the cathode 18 oftube 19 for the ,same purpose..- The tubes 16 and 19 are preferably similar to the tube 3 of Fig. 1'. A third winding 20 has one terminal connectedwith the winding 17 and the other terminal with the anode oftube 16. The cathode 15 is connected with the inductance 2-1, which in turn is connected with the impedance 22 and also with the condenser 23, which serves to hold a large charge of electricity. Another condenser 24: is connected in parallel with condenser 23 between the cathode 15. and the cathode 18 A condenser 25 is connected across the anode and cathode of the tube 19, and the stopping condensers 26 and 27 are connected in series with the alternating current output circuit.

Themanner in which the circuit above described functions in order to convert the' "frequency of an alternatlng current is as follows: When a potential is applied by the source 11 across the winding 12 of trans- 'nating former 13, the cathodes 15 and 18 of tubes 16 and 19 will be energ'z'ed. When the voltage applied to the winding 20 is in such direction as to render the anode of tube 16 positive with respect to the cathode, current will flow through the said tube, and a dif- A ference of potential will be created across the condenser 24- and also across the condenser 23 in series with the inductance 21. The

tube 16' thus acts as a half-wave rectifierr'fli The application of these rectified impulses to the condenser 23 will gradually build up a large charge across the plates of this condenser. The inductance 21 and the condenser 2 1 serve as a filter to reduce to a minimum the effects of the alternating component.u p0n the condenser 23 which serves as a reservoir for the direct current impulses. This latter condenser, as will be seen from the drawing, applies its voltage.

across theelectrodes of the tube 19 and also across the plates of condenser 25. When the voltage of'condenser 23 becomes sufficiently great to break down the gap of tube 19, os-

cillations will be set up which will produce an alternating current of the desired frequency for transmission over the output circuit. The manner in which theelements 19,

22 and 25 function to produce an alternatingcurrent of the desired frequency is the same as in Fig. 1. The principal difference between the arrangements shown in Figs. 1 and 4: resides in the primary source of energy. Thus in Fig. 1 the direct current source may consist of a battery or a direct current generator. In Fig. 4 the direct current necessary for the operation of the converting apparatus is derived from an alternating current source. The arrangements shown in the figures of the drawing are simply .illustrative of some ways for applying the invention. It 1's, of course, obvious that other and ilfifiBI'eIll; ways will occur to those skilled in e art.

It will, therefore, be apparent that systems such as have been described, em loying a. helium filled tube having electrodbs of the preferred type mentioned above, constitutes slmple and efficient means either for deriving alternating potentials from a direct'current potential, or for converting an altercurrent from one frequency to another. 4

While this invention has been disclosed as embodied in a particular form it is to be understood thatit is capable of embodiment 1111011181 forms without departing from the spirit and scope of the appended claims.

What is claimed is:

1. In a frequency changing system, the

combination with a source of alternatin current of fixed frequency, of a gas filled tube having an anode and a heated cathode, the said anode being connected with one side of the said source, and the said cathode with 139 the other side, the later connection including a condenser of relatively large" calpacity to be charged by the rectified imp ses produced by the said tube, a second gas filled tube having an anode and a heated cathode eifectively connected across said condenser,

4 combination with a source of alternating ,current of known fixed frequency, of a rectifier connected therewith, a condenser of relatively low'capacity connected with the rectifier to be charged *thereby, the connection including a filter to substantially eliminate alternating current components of the rectified current, a gas filled tube having an anode and a heated cathode eflectively bridged across said condenser, the

anode connection including an impedance, a

second condenser bridged across the electrodes of the said gas filled tube, and an output circuit connected with the said second condenser,"'the value of the said impedance being such that the voltage drop therethrough will stop the discharge of the said second tube when the char e taken by the said second condenser reac es a predetermined value, whereb the frequency of the oscillations is control ed.

. 3. In ,a frequency changing system, the combination with a source of alternating current, er a transformer havin a primary winding connected with the sad source and a lurality of secondary windings, a gasv filed rectifying tube having its cathode connected across one ofsaid secondary windings to activate said cathode and having its anode connected with one terminal of a second secondary winding, a condenser of relatively large capacity connected with the said rectifying tube, the connection including a filter'to smooth out the rectified wave,-a

second gas filled tube having an anode and a cathode, which electrodes are eifectivelybridged across the said condenser, the anode connection including an impedance, the cathode being bridged across a third secondary winding of said transformer to which is also connected the other terminal of the said second secondary winding, a second condenser bridged across the e ectrode of the second tube, and an output circuit connected with the said second condenser, theiw'alue of the, said impedance being suchithat the a voltage drop therethrough will stopthe discharge of the said second tube when the charge taken by the said second condenserreaches a predetermined value, whereby the frequency of the oscillations is controlled;

In testimony whereof, I have signed my name to this specification this lath day of November, 1924. I

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